Question

Write short notes on Sintering.

Answer 1

Sintering:

• During this step, the green compact is heated in a protective atmosphere furnace to a suitable temperature, which is below the melting point of the metal.
• Typical sintering atmospheres are endothermic gas, exothermic gas, dissociated ammonia, hydrogen, and nitrogen.
• Sintering temperature varies from metal to metal; typically these are within 70 to 90% of the melting point of the metal or alloy.

• Sintering is a solid state process which is responsible for producing physical and mechanical properties in the PM part by developing metallurgical bond among the powder particles.
• It also serves to remove the lubricant from the powder, prevents oxidation, and controls carbon content in the part.
• The structure and porosity obtained in a sintered compact depend on the temperature, time, and processing details.
• It is not possible to completely eliminate the porosity because voids cannot be completely closed by compaction and because gases evolved during sintering.
• Porosity is an important characteristic for making PM bearings and filters.